1. Field of the Invention
The present invention relates generally to the field of pumps that are used to pump fluids from oil wells and the like, and more particularly but not by way of limitation to an improved valve assembly for use with such downhole pumps.
2. Prior Art
There have been a number of prior art patents that teach the basics of problems encountered in downhole pumping processes. An early teaching of a downhole pumping device is U.S. Pat. No. 456,128 issued to Darling in 1891. The Darling patent teaches the combination of check valves with a lower trap valve assembly. A later example, Lindgren's U.S. Pat. No. 2,363,343, issued Nov. 21, 1944, discusses the gas locking phenomenon encountered with gaseous fluids when using conventional traveling valves that have ball check valves. While numerous improvements in traveling valves have been made over the years since Lindgren's early teaching, the problems addressed by him remain largely unsolved.
Particularly, valve assemblies associated with downhole pumps continue to present serious difficulties, including gas lock and fluid pounding, as well as problems encountered with downhole particulates and corrosion. A recent valve assembly sold by Spears Oil Tool, Inc. of Tomball, Tex., features a rotary spindle that alternately opens and closes fluid flow ports by the operation of a traveling guide which is reciprocated by the valve rod connected to surface equipment, the guide coacting with a screw rod that extends from the spindle member. The rotational positions of the barrel member blocks or opens the ports in the housing.
It appears that the Spears device, like other similar valves, does reduce gas leaking under ideal conditions, but such ideal conditions are rarely encountered in a subsurface reservior. Difficulties remain, including those associated with back flowing particulates, such as sand and the like, and with corrosion. Also, the free travel of moving parts in most traveling valves, including the guide member of the Spears device, is frequently hindered when operated in a tilted position as where the oil well bore is not disposed vertically from the ground's surface, a condition often found in a downhole environment.